Adjusting means for intermediatefrequency transformers



March 3, 1936. M. J. KIRK 29% 9 ADJUSTING MEANS'FOR INTERMEDIATE FREQUENCY TRANSFORIIKFRS Filed Jan. 23, 1935 INVENTORS J05EPH C M G/N X BY MAET/NJ /(/,K,

yam-M W/ ATTORNEY.

Patented Mar. 3, 1936 UNITED STATES PATENT OF-FZQE ADJUSTING MEANS FOR INTERMEDIATE- FREQUENCY TRANSFORMERS Martin J. Kirk, Chicago, and Joseph C. McGinley, Hinsdale, Ill., assignors to Johnson Laboratories, nois Inc., Chicago, 111., a corporation of Illi- Application January 28, 1935, Serial No. 3,710

6 Claims. (Cl. 171-119) The condensers are normally of a type having very low losses, and include means for a small adjustment of the capacity values. The efficiency of the complete design depends to a very large extent upon the inductors.

An object of this invention is to provide improved means ior' adjusting the coupling in a transformer for such systems. The present invention is particularly adapted for application to transformers of the general type herein described and illustrated, but it is equally as well adapted for use onother types of transformers of similar design.

In present-day designs, transformers of the class here under consideration normally have air cores. Across the primary and also across the secondary, there is connected a condenser whose I capacity is adjustable over a limited range. By

suitably designing the primary and secondary in= ductors and by adjustment of the associated condensers, each of the circuits may be tuned to be resonant at the desired frequency. In order to effect a maximum transfer of energy between the primary and the secondary, it is essential that the electromagnetic coupling between the two inductors shall be closely oi the optimum value. In present designs, it is normal to establish the degree of coupling in the design of the transformer, so that when the inductors are assembled, the proper coupling will exist.

Because of the losses which normally exist in air-core inductors of the type now commonly used, it is not essential to provide means for adjusting the coupling-between the primary and secondary after the unit is assembled. It is usually sufllcient to determine experimentally what physical relation between'the two inductors will give approximately the correct coupling and then to mechanically design the transformer so as to produce this relation.

In transformers of the improved type herein described, the losses in the inductors themselves are greatly decreased, and it therefore becomes.

desirable to provide means for accurately adjusting each transformer to the desired coupling between primary and secondary. Previous methods for securing this adjustment have had certain disadvantages and limitationsr For instance, the adjustment can not be made without the applica:

tion of heat to melt the binder employed to hold the movable inductor in a desired position; or it is necessary to make the adjustment before the complete transformer is mounted on th chassis of the equipment in which it is to be employed. An important further disadvantage, in view of the critical adjustment of coupling required, is the lack of a tamperproof means for locking the movable coil in the correct position after the ad justment is made.

The present invention provides means for ac-= curately adjusting the coupling from without the shield can in which the transformer is mounted and, in addition, simple and positive means for locking the movable inductor in the correct position. The improved method or" the present invention requires a minimum number of parts does not appreciably increase the cost of manufacture of the transformer.

The invention will be better understood by reference to the drawing, in which:

Figure l is an elevation of an intermediate frequency transformer incorporating present invention;

Figure 2 is a detail, partly in section, of the lower portion of the transformer shown ure 1;

Figure 3 is a detail taken in a direction at right angles to the view shown in Figure 2;

Figure l is a section on the line E -t of Figure 2; and p Figure 5 is a section on the line 5-5 of Figure 2.

Referring to Figure l, the transformer consists of insulating base i, on which. are mounted insulating frame 2 and adjustable condensers 3 and 63. Frame 2 in turn supports coils 5 and 8, mounted on their respective tubular magnetic cores l and 8. Core I is secured to the insulating rod 9 which is rigidly attached to frame 2. Core 8 is secured to the insulating rod I!) which is arranged to be moved in the direction of its axis relative to frame 2, and to be secured in adjusted position by set screw l I. The whole transformer is mounted in shield can I2, which is provided with a suitable hole I3 to permit accessto adjusting nut l4. Adjusting nut H is locked in positi'on by set screw 1 5, and holes are provided in the chassis to which the transformer is to be attached to permit access,to set screws H and i5 after assembly,

The adjustable mounting for cell 6 and core 8 is shown in detail in Figures 2 to 5, incluisve. The protruding end of rod Ill is square, and fits freely into a square hole in the corresponding portion of frame 2. The remainder of rod I0 is round,'and fits snugly into tubular core 8. A

- threaded male member or insert I6 is molded ofrod ID. The female member or adjusting nut maintained in substantially fixed axial position relative to the corresponding portion of frame 2 by means of set screw I5, the pointed end of which engages a V-shaped groove I9 in the integral collar portion of nut Id. The range of adjustment obtainable is limited on the one hand when core 8 strikes frame 2, and on the other hand when nut I1 strikes frame 2, and thus the adjustment is stopped before any parts come free from the assembly.

In operation, set screws II and I5 are loosened slightly, and then nut I4 is turned until coil 6 is in the desired position relative to coil 5. Final- 1y, set screws I5 and II are firmly tightened, preferably in this order, so as to prevent any strain from being placed on frame 2 due to set screw I5 first contacting nut I4 on one side of the groove I9 instead of at its center, as might occur in the event that set screw I5 had been loosened more than barely necessary to free adjusting nut Hi.

It will be noted that the present invention provides means for locking the adjusting mechanism as well as.for locking the movable inductor in the proper position. Thus there is provided a safeguard against unauthorized tampering with the setting of adjusting nut I4, which is accessible from the top side of the chassis. Such tam,-

pering would cause a strain on frame 2, whether .or not it produced any motion of the movable inductor 6, 8.

It is to be understood that the application of I this method of adjustment to other similar types of transformers or the employment of modifications such as might readily occur to a person skilled in the art fall within the scope of the present invention. The embodiment shown is merely by, way of an example of one application of the invention, and is not intended as a limitation on its scope, which is as set forth in the following claims.

Having thus described our invention, what we claim is:

1. In a-high-frequency transformer having at least two inductors, an insulating frame for supporting said inductors and means for adjusting the position of one of said inductors relative to another of said inductors, said means including an insulating rod upon which said adjustable inductor is secured, said rod having a male screwthreaded member secured in and projecting from one end thereof, the other end of said rod being of non-circular cross-section and being journaled in a hole in said frame to permit axial motion but to prevent rotation thereof, a female screw-threaded member journaled in a second hole in said frame and having a peripheral groove and a head by which it may be rotated, a lock-screw projecting into the groove in'said female member to prevent axial motion thereof and to lock said female member in adjusted position, whereby rotation of said female member produces axial motion of said adjustable inductor.

least two inductors, an insulating frame for supporting said inductors, and means for adjustiu able inductor is secured,'said rod having a 2. A high-frequency transformer having at Hi also screws onto threaded insert I6, and is male screwthreaded member secured in and projecting from one end thereof, the other end of said rod being of non-circular cross-section and being journaled in a hole in said frame to permit axial motion but to prevent rotation of said rod, said adjustable inductor being clamped on said rod against projections thereon by a nut on said male member, a female screwthreaded member journaled in a second hole in said frame and having a peripheral groove and a head whereby it may be rotated, a lock-screw in said frame projecting into said groove to prevent axial motion of said female member and to lock it in adjusted position, said female member coacting with said male member whereby rotation of said female member produces axial motion of said adjustable inductor, and a second lock screw in said frame adapted to clamp said rod in adjusted position.

3. In a high-frequency transformer having at least two inductors, each of said inductors including a magnetic core, an insulating frame for supporting said inductors and means for adjusting the position of one of said inductors relative to another of said inductors, said means including an insulating rod upon which said adjustable inductor is secured, said rod having a male screwthreaded member secured in and projecting from one end thereof, the other end of said rod being of non-circular cross section and being journaled in a hole in said frame to permit axial motion but to prevent rotation of said rod, said adjustable inductor being clamped on said rod against projections thereon by a nut on said male member, a female screwthreaded member journaled in a second hole in said frame and having a peripheral groove and a headwhereby it may be rotated, a'lock screw in said frame projecting into said groove to prevent axial motion of said female member and tolock it in adjusted position, said female member coacting with said male member whereby rotation of said female member produces axial motion of said adjustable inductor, a second lock screw in said frame adapted to clamp said rod in adjusted position, and a conductive shield surrounding said. transformer, said shield being provided with an opening permitting access, to said female member.

4. A high-frequency transformer, including an insulating frame, a magnetic core carried by said frame, a further and movable magnetic core also carried by said frame, coils carried by said cores, a screw for longitudinally adjusting said movable core, a nut for actuating said screw, and an adjustable detent for preventing rotation of said nut.

5; A high-frequency transformer, including an insulatingframe, a magnetic core carried by said frame, a further and longitudinally movable magnetic core extending through a wall of said frame, a set screw engaging said core, and coils respectively carried by said cores.

6. A high-frequency transformer, including an insulating frame having a polygonal opening in a wall thereof, a magnetic core carried by said frame, a further and longitudinally-movable magnetic core having a polygonal end which extends through said polygonal opening, and coils respectively carried by said cores.

MARTIN J. KIRK. JOSEPH c. McGINL-EY. 

